1. Field of the Invention
The present invention relates to a method of radio resource allocation and related communication apparatus, and more particularly, to a method for avoiding radio resource waste in a wireless communication system and related communication apparatus.
2. Description of the Prior Art
According to Medium Access Control (MAC) protocol specification defined by the 3rd Generation Partnership Project (3GPP), MAC layer, a lower layer of a Radio Link Control (RLC) layer, supports functions of mapping between logical channels and transport channels, multiplexing, de-multiplexing, logical channel prioritization, transport format selection, and so on. The MAC layer exchanges RLC PDUs (Protocol Data Units), namely MAC SDUs (Service Data Units), with the RLC layer via logic channels and exchanges MAC PDUs with a physical layer via transport channels, such as an uplink shared channel (UL-SCH) or a downlink shared channel (DL-SCH).
In the MAC layer, a logical channel prioritization procedure is applied when a new transmission is performed. Each logical channel is given a Prioritized Bit Rate (PBR), which is a rate like X bytes/s or Y bits/s. The logical channel prioritization procedure ensures that all the logical channels are served in a decreasing priority order up to their configured PBR.
In a word, the logical channel prioritization procedure of the MAC layer is that the logical channels transmit data to the MAC layer in a TTI according to a priority, so the data with higher priority could be transmitted early.
Further illustrate the logical channel prioritization procedure, to clearly explain resource allocation and data transmission process. When a user equipment (UE) performs uplink transmission, network of the wireless communication system allocates a grant to UE, for providing radio resource. The grant is a largest data amount allowed UE to transmit. Then, the Radio Resource Control (RRC) layer of the UE gives each logical channel a priority and a PBR, to allocate resource to each logical channel according to the decreasing priority order. The largest resource amount allocated to each logical channel cannot exceed PBR.
In addition, the prior art provides a PBR token bucket framework for calculating allowed resource amount of the plurality of logical channels. The PBR token bucket framework uses a PBR token bucket parameter and a PBR token rate. The PBR token bucket parameter is used for indicating the resource amount allowed the logical channels to use, and the PBR token rate is used for indicating the number of bytes added to the PBR token bucket parameter of the logical channel at every TTI.
At every TTI, UE executes PBR token bucket framework, including adding the PBR token rate to the PBR token bucket parameter, for increasing allowed resource amount for the logical channels, allocating resource to the logical channels with the PBR token bucket parameter larger than zero according to the decreasing priority order, and decreasing the PBR token bucket parameter and the grant according to the resource amount allocated to the logical channels.
In the prior art, when the allowed resource amount of the logical channel is insufficient (namely the PBR token bucket parameter of the logical channel is smaller than the data amount), the logical channel just can be allocated the same resource amount with the resource amount which can be used for the logical channel. Meanwhile, the PBR token bucket parameter is decreased to be zero (namely there is no resource can be used for the logical channel), so the logical channel cannot be allocated resource anymore. Therefore, if all the logical chancels having data available for transmission cannot perform resource allocation anymore, these logical channels cannot transmit data even the grant remains, which causes radio resource waste.
Note that, the RRC layer further gives each logical channel corresponding to a Guarantee Bit Rate (GBR) bearer a Maximum Bit Rate (MBR), which is a rate like X bytes/s or Y bits/s. MBR is given according different QoS services; for example, Voice over Internet Protocol (VoIP) service is a transmission by the GBR bearer.
Take the RRC layer gives each logical channel a PBR, MBR and priority as an example. According to the configured PBR, the logical channels perform resource allocation according to the decreasing priority order. Then, if the grant remains, according to the configured MBR, the logical channels perform resource allocation according to the decreasing priority order. After that, the logical channels still having data available for transmission cannot perform resource allocation anymore even if the grant remains, causing waste of radio resource.
In addition, in the prior art, besides utilizing PBR token bucket framework for calculating the allowed resource amount of each logical channel, the MBR token bucket framework is utilized for calculating allowed resource amount of the logical channels also. The MBR token bucket framework uses a MBR token bucket parameter and a MBR token rate. The MBR token bucket parameter is used for indicating the resource amount allowed the logical channels to use, and the MBR token rate is used for indicating the number of bytes added to the MBR token bucket parameter of the logical channel at every TTI.
In the prior art, UE initiates the PBR token bucket framework, and then initiates the MBR token bucket framework at every TTI. The PBR token bucket framework has been described above, so the detailed description is omitted herein. After that, UE performs the PBR token bucket framework, including adding the MBR token rate to the MBR token bucket parameter, if the grant for UE remains and logical channels still have data available for transmission, allocating resource to the logical channels with the MBR token bucket parameter larger than zero (namely added MBR token rate) according to the decreasing priority order, and decrease the MBR token bucket parameter and the grant according to the allocated resource amount. After that, the logical channels still having data available for transmission cannot perform resource allocation anymore even if the grant remains, causing radio resource waste.
As can be seen form above, after UE performs MBR token bucket framework, the logical channel prioritization procedure of the prior art does not disclose the operating method, which causes the logical channels to be incapable of allocating resource even if the grant remains. In addition, when a logical channel does not have allowed resource amount (namely the MBR token bucket parameter is zero), the logical channels cannot perform resource allocation anymore even if the grant for UE remains, causing the radio resource waste.
Therefore, in the prior art, after UE performs PBR and MBR token bucket framework, the logical channels still having data available for transmission cannot perform resource allocation anymore even if the grant remains. Since the logical channels cannot perform resource allocation, the logical channels cannot transmit data, causing resource waste. In addition, if the allowed resource amount of the logical channels is smaller than the data amount, since the logical channels need more resource for transmitting data, the data will be transmitted in different TTI. Therefore, the uplink transmission for the PDUs is delayed and affecting efficiency of the wireless communication system.